// stdmove.cpp -- using std::move()
#include <iostream>
#include <utility>

// interface
class Useless {
private:
    int n;          // number of element
    char *pc;      // pointer to data
    static int ct;  // number of objects
    void ShowObject() const;
public:
    Useless();
    explicit Useless(int k);
    Useless(int k, char ch);
    Useless(const Useless &f);  // regular copy constructor
    Useless(Useless &&f);  // move constructor
    ~Useless();
    Useless operator+(const Useless &f) const;
    Useless &operator=(const Useless &f);   // copy assignment
    Useless &operator=(Useless &&f);        // move assignment
    void ShowData() const;
};

// implementation
int Useless::ct = 0;

Useless::Useless() {
    ++ct;
    n = 0;
    pc = nullptr;
}

Useless::Useless(int k) : n(k) {
    ++ct;
    pc = new char[n];
}

Useless::Useless(int k, char ch) : n(k) {
    ++ct;
    pc = new char[n];
    for (int i = 0; i < n; ++i)
        pc[i] = ch;
}

Useless::Useless(const Useless &f) : n(f.n) {
    ++ct;
    pc = new char[n];
    for (int i = 0; i < n; ++i)
        pc[i] = f.pc[i];
}

Useless::Useless(Useless &&f) : n(f.n) {
    ++ct;
    pc = f.pc;  // steal address
    f.pc = nullptr; // give old object nothing in return
    f.n = 0;
}

Useless::~Useless() {
    delete[] pc;
}

// copy assignment
Useless & Useless::operator=(const Useless &f) {
    std::cout << "copy assignment operator called:\n";
    if (this == &f)
        return *this;
    delete[] pc;
    n = f.n;
    pc = new char[n];
    for(int i = 0; i < n; ++i)
        pc[i] = f.pc[i];
    return *this;
}

// move assignment
Useless & Useless::operator=(Useless &&f) {
    std::cout << "move assignment operator called:\n";
    if (this == &f)
        return *this;
    delete[] pc;
    n = f.n;
    pc = f.pc;
    f.n = 0;
    f.pc = nullptr;
    return *this;
}

Useless Useless::operator+(const Useless &f) const {
    Useless temp = Useless(n + f.n);
    for (int i = 0; i < n; ++i)
        temp.pc[i] = pc[i];
    for (int i = n; i < temp.n; ++i)
        temp.pc[i] = f.pc[i - n];
    return temp;
}

void Useless::ShowObject() const {
    std::cout << "Number of elements: " << n;
    std::cout << " Data address: " << (void *) pc << std::endl;
}

void Useless::ShowData() const {
    if (n == 0)
        std::cout << "(object empty)";
    else
        for (int i = 0; i < n; ++i) std::cout << pc[i];
    std::cout << std::endl;
}

// application
int main() {
    using std::cout;
    {
        Useless one(10, 'x');
        Useless two = one + one;    // calls move constructor
        cout << "object one: ";
        one.ShowData();
        cout << "object two: ";
        two.ShowData();
        Useless three, four;
        cout << "three = one\n";
        three = one;    // automatic copy assignment
        cout << "now object three = ";
        three.ShowData();
        cout << "and object one = ";
        one.ShowData();
        cout << "four = one + two\n";
        four = one + two;   // automatic move assignment
        cout << "now object four = ";
        four.ShowData();
        cout << "four = move(one)\n";
        four = std::move(one);  // forced move assignment
        four.ShowData();
        cout << "and object four = ";
        four.ShowData();
        cout << "and object one = ";
        one.ShowData();
    }
    return 0;
}
